A message on the lips.

F ew systemic diseases present with such a diversity of cardiopulmonary manifestations as hereditary haemorrhagic telangiectasia (HHT), also known as Osler’s disease or Rendu–Osler–Weber syndrome. HHT is one of the most common inherited diseases, with a prevalence of one in 5,000–10,000, and has been linked to mutations in at least five different genes, including endoglin and activated-receptor-like kinase (Alk)-1, both belonging to the transforming growth factor (TGF)-b superfamily of receptors [1]. Alk-1 and endoglin are abundantly expressed on endothelial cells and are involved in mediating the cellular effects of TGF-b and other members of the TGF-b superfamily. Loss-of-function mutations in the genes encoding for Alk-1 or endoglin cause the clinical syndrome of HHT, which is characterised by vascular dysplasia. The cardinal clinical features of HHT include mucocutaneous telangiectases, often prominently visible on the lips and tongue, and arteriovenous malformations (AVMs), which can involve several organs, such as liver, brain and lungs. Pulmonologists will encounter three main manifestations of HHT: pulmonary arterial hypertension; high cardiac output failure in the setting of large AVMs in the liver; and pulmonary AVMs. A forthcoming article by FAUGHNAN et al. [2], as part of the European Respiratory Journal’s (ERJ) current series on pulmonary hypertension [2–7], will review the cardiopulmonary manifestations of HHT in detail.